Optical position detecting device

ABSTRACT

In a relative angle detecting device, plural received light outputs are subjected to time division. Received light detection voltage is shifted by a phase shifter and sampling pulse is formed, and peak detecting means holds peak value of received light output based on the sampling pulse. In a CPU, peak value of each voltage is stored in a memory, and the stored value is operated thereby information regarding relative position between a light source and a light reception element is operated. Utilizing the time division, each received light detection voltage can be processed in the same condition, and the peak value of each received light output can be detected with high precision.

This application is a division of application Ser. No. 08/498,862, filedJul. 6, 1995, now U.S. Pat. No. 6,028,592.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a relative angle detecting device wheredifference and sum of received light outputs in light receiving sectionsdivided in two or more are operated, and data regarding a relativeposition between a light source and a light receiving section areoperated, and, for example, a relative position between an input devicehaving the light receiving section and a device body such as a computeror a game device, having the light source is detected and the coordinateinput or the like to the device body becomes possible.

2. Prior Art

FIG. 9 shows a remote input device as an example of a device using arelative angle detecting device which uses a light source and a lightreceiving section and detects a relative position between both sections.

In the remote input device, coordinate information or the like can beinputted from an input device 3 to a screen 1 provided on a device bodysuch as a computer or a game device, and configuration of the remoteinput device is the same as that disclosed in the specification anddrawings of JPA 317479/1993.

In FIG. 9, numeral 1 designates a CRT screen provided on a device body,such as a computer, an AV device, a game device or the like. A lightemitting device 2 is fixed on the CRT screen 1, and a light source 2aemitting a reference light is installed to the light emitting device 2.

The input device 3 can be moved freely within a space of a positionremote from the screen 1, and a detecting section 4 having structureshown in FIG. 10 is installed on the top end of the input device 3. Thedetecting section 4 is provided with a reception element 5, and adiaphragm 6 and a visible light cut filter 7 are installed in front ofthe reception element 5.

If the optical axis orthogonal to the aperture center of the diaphragm 6is assumed as Z-axis, the Z-axis becomes axis directed along the centerof the input device 3 towards the front thereof. As shown in FIG. 11,the reception element 5 is constituted by pin photo diodes having lightreceiving sections 5a, 5b, 5c, 5d divided in four. Taking the X-Yorthogonal coordinates being orthogonal to the Z-axis, set of the lightreceiving sections 5a, 5b and set of the light receiving sections 5c, 5dare divided in the Y-axis direction, and set of the light receivingsections 5b, 5d and set of the light receiving sections 5a, 5c aredivided in the X-axis direction.

The diaphragm 6 has a rectangular aperture, and infrared light emittedfrom the light source 2a is irradiated as rectangular spot light α tothe reception element 5. In respective light receiving sections 5a-5d, adetection current is obtained based on the irradiation area of the spotlight α. Provided that detection outputs based on the irradiation areaof the spot light in the light receiving sections 5a-5d are Lu, Ru, Ld,Rd respectively, regarding respective detection outputs, difference ofreceived light outputs in set of the light receiving sections divided inthe Y-axis direction and difference of received light outputs in set ofthe light receiving sections divided in the X-axis direction areoperated, thereby inclination in the two-dimensional direction (θx, θy)of the Z-axis extending in the front of the input device 3 can beestimated.

Based on the inclination (θx, θy), a cursor mark 8 displayed in thevicinity of the intersection to the Z-axis on the screen 1 is moved onthe X-Y coordinates, and the moved amount is transmitted as the X-Ycoordinate data or as information data of the inclination (θx, θy),thereby the information data regarding the direction of the input device3 with respect to the device body are given to the device body. At. theside of the device body, the cursor mark 8 is displayed based on thereceived data and is moved according to the direction of the inputdevice 3. Also drawing to the screen 1 becomes possible.

In a relative angle detecting device used in the remote input device asabove described, difference and sum of the received light outputs Lu,Ru, Ld, Rd by the 4-divided light receiving sections 5a, 5b, 5c, 5dshown in FIG. 11 must be estimated, but for the estimation, receivedlight outputs from the 4-divided light receiving sections must beobtained concurrently. Consequently, in each light receiving section, aprocessing circuit-comprising a current/voltage converter, an amplifier,a band pass filter and the like is required.

When the processing circuit is installed separately in each lightreceiving section, however, if characteristics of the circuit elementsconstituting respective processing circuits are not coincident, ratio ofthe received light outputs in respective light receiving sections cannotbe obtained correctly. Consequently, electronic parts are selected andcircuit adjustment is carried out so that characteristics of the circuitelements installed in respective light receiving sections arecoincident. However, the work therefor becomes very difficult, and as aresult, it is impossible that characteristics of the respectiveprocessing circuits be coincident completely. Consequently, dispersionof the characteristics of the processing circuits is allowed, andcorresponding to this, allowable deviation in parts other than theprocessing circuit becomes strict and therefore the high precision ofthe device as a whole is inhibited.

Also in various devices obtaining signals by received light outputs of areception element, in general, a variable gain amplifier for amplifyingreceived light outputs from the reception element is installed, and autogain control is carried out in that gain of the variable gain amplifieris controlled in response to the intensity of the received lightoutputs. However, in a relative angle detecting device which must obtainreceived light outputs different from each other in the intensity alwaysfrom the light receiving sections 5a, 5b, 5c, 5d shown in FIG. 11, ifthe amplification gain is controlled in each processing circuit providedin each light receiving section, ratio of the light receiving area ineach light receiving section cannot be grasped correctly. Consequently,the gain must be controlled equally to the received light output fromeach light receiving section, and the circuit configuration for the gaincontrol of the received light output is complicated inevitably.

SUMMARY OF THE INVENTION

In order to solve the above-mentioned problems in the prior art, anobject of the present invention is to provide a relative angle detectingdevice that a plurality of received light outputs can be processed inprocessing circuits having the same characteristics, so that ratio ofthe plurality of received light outputs can be obtained with highprecision.

Another object of the present invention is to provide a relative angledetecting device that in time division of a plurality of received lightoutputs, timing of the time division can be set with high precisionusing a simple circuit.

Still another object of the present invention is to provide a relativeangle detecting device that when light from a light source with theintensity varying in prescribed frequency is received, the peak value ofthe received light output can be detected in timing with high precision,and also when a plurality of received light-outputs are obtained in timedivision, the peak value can be detected at the stable state of thereceived light outputs thereby the peak value of the received lightoutputs can be detected correctly.

A relative angle detecting device according to the present inventioncomprises a light receiving section for detecting light from a lightsource, a switch for changing and outputting a plurality of receivedlight outputs in definite period, detecting means for detectingindividual received light outputs changed by the switch, and arithmeticmeans for operating data regarding a relative position between the lightsource and the light receiving section from the individual receivedlight outputs detected by the detecting means.

For example, the light receiving section is installed at an input devicewith the direction variable, and a reference light from a light sourceinstalled at the device body having a screen is received by the lightreceiving section, and the received light output from each lightreceiving section is operated in the arithmetic means therebyinformation regarding the detection of the input device with respect tothe device body can be calculated. The information calculated in thearithmetic means of the input device is supplied to the device bodythereby a cursor mark or the like can be displayed on the screen of thedevice body or the mark can be moved.

In the detecting means as above described, the received light outputschanged by the switch mean both the case that received light outputs ledrespectively from the light receiving section are changed and the casethat a plurality of received light outputs as a result of adding orsubtracting any of received light outputs from the light receivingsection are changed.

In the above-mentioned configuration, the peak value of the receivedlight outputs is detected in the detecting means, and data regarding therelative position are processed based on the peak value in thearithmetic means.

Or, the peak value and the bottom value of the received light outputsare detected in the detecting means, and operation regarding therelative position is carried out based on the value of differencebetween the peak value and the bottom value in the arithmetic means.

Also a waveform shaping section for shaping waveform of the receivedlight output and generating the reference signal may be installed, andthe reference signal may be counted and the detection timing of thedetecting means may be calculated in a CPU, and the received lightoutput may be detected in the detecting means based on the timingcommand from the CPU.

Also when the detecting means is that other than the CPU, the detectedvalue is supplied through an analog/digital converter to the arithmeticmeans.

Also the detecting means and the arithmetic means may be included in theCPU, and respective operations may be executed by software.

Also a waveform shaping section for shaping waveform of the receivedlight outputs and switch changing means for counting the referencesignal with the waveform shaped and for changing the switch based on thecounted value may be installed.

In the above-mentioned configuration, the switch changing means and thearithmetic means may be included in the CPU, and respective operationsmay be executed by software.

Or, a variable gain amplifier for amplifying the received light outputsmay be installed at the stage of the detecting means, and respectivereceived light outputs may be added in the CPU, and based on the addedvalue, gain of the variable gain amplifier may be controlled.

Further, respective received light outputs may be added in the CPU, andbased on the added value, the emitted light amount of the light sourcemay be controlled.

Also as a concrete circuit configuration, a phase shifter for shiftingphase of individual received light outputs changed by the switch, and awaveform shaping section for shaping the output waveform of the phaseshifter into rectangular wave, and a trigger circuit for reducingwavelength of the rectangular wave may be installed, and in thedetecting means, the received light outputs at the fall state of thereduced rectangular wave may be held as the detected value.

Or, the relative angle detecting device may be provided with a waveformshaping section for shaping waveform of the received light outputs, aswitch changing section for counting the reference signal with thewaveform shaped and for changing the switch every time the count numberbecomes the prescribed number, a phase shifter for shifting phase of theindividual received light outputs changed in the switch, a waveformshaping section for shaping the output waveform of the phase shifterinto rectangular wave, and a trigger circuit for reducing wavelength ofthe rectangular wave, where the detection allowance signal may beoutputted from the switch changing section when the reference signalbecomes the prescribed number after the switch is changed, and in thedetecting means, the received light outputs are held as the detectedvalue when the allowance signal is outputted and the rectangular wavereduced in the trigger circuit falls.

Further, the relative angle detecting device of the present inventioncomprises an information processing device of controlled type and aninput device, and the information processing device of controlled typeis provided with a light emitting section, a display section and a lightreceiving section, and the input device is provided with a receptionelement for receiving light from the light emitting section, a pluralityof current/voltage converters for converting an output. signal of thereception element into voltage, a changing circuit for selecting outputvoltages of plural channels obtained in the plurality of current/voltageconverters in time division in response to the channel changing signaland for generating the time division output voltage, a signal processingsection for processing the time division output voltage and forgenerating relative angle data, a voltage level detecting section fordetecting voltage level of each channel in the time division outputvoltage, and a control unit for operating and calculating the relativeangle data and forming coordinate signals and for transmitting thecoordinate signals to the light receiving section, where the controlunit is provided with means for supplying the channel changing signal ofnext time to the changing circuit so that channels are selected in theorder of the amount of voltage level of each channel detected in thevoltage level detecting section.

In the above-mentioned means, received light outputs led from individuallight receiving sections or received light outputs of plural setsobtained as a result of addition or subtraction of respective receivedlight outputs of plural light receiving sections are changed by a switchand outputted in order from the switch in definite period. Theindividual received light outputs changed in the switch are processed inthe common processing circuit. Consequently, ratio of the received lightamount in respective light receiving sections can be detected correctlyin comparison with that having a separate processing circuit in eachreceived light output. In respective received light outputs changed inthe switch, the value detected by the detecting means is held andoperation is carried out.

Received light outputs are inputted to the arithmetic means in order inresponse to the switch changing period. In the arithmetic means,respective received light outputs (the peak value or the peak value andthe bottom value) are stored in the internal memory or the externalmemory, and operation is carried out based on respective stored values.As a result of the operation, data regarding the relative positionbetween the light source and the light receiving section are calculated.

As a result, for example, when the light receiving section is installedat the input device and the light source is installed at the device bodyhaving a screen, if the input device is moved on the space, thedirection of the input device with respect to the screen of the devicebody can be operated as data of the inclination angle (θx, θy) or asdata on the X-Y coordinates in parallel to the screen. If the operationresult is transmitted to the device body by wire telegraphy or radiotelegraphy, display on the screen is varied in response to the directionof the input device in the device body. Thereby the moving input of thecursor or the drawing input becomes possible on the screen.

Also added value of the received light outputs before changed in theswitch or the received light outputs changed by the switch and passingthrough the band pass filter are subjected to the waveform shaping.Thereby a reference signal (reference clock) is generated based onreceived light outputs of light transmitted from the light source inconstant frequency with the intensity varying. In the switch changingsection or the CPU, the reference signal is counted and a changingsignal is generated every time the count number becomes the prescribednumber, and the received light output voltage is changed in the timingof the changing signal by the switch. That is, since the referencesignal (reference clock) is generated from the received light output, anoscillation circuit for generating separate clock or the like is notrequired. Also since the switch is changed based on the referencesignal, the switch changing grasps the period of the received lightoutput voltage correctly and length of the received light output voltageafter changed by the switch is set with high precision.

Further since the detection timing of the received light output from thesynchronous circuit or the CPU to the detecting means is commanded basedon the reference signal, the received light output (the peak value orthe peak value and the bottom value) is detected with high precision.

Also when a variable gain amplifier for amplifying the received lightoutput is installed at the front stage of the detecting means, storedvalues of the respective received light outputs are added and gain ofthe variable gain amplifier is controlled by the added result in thearithmetic means. The stored values are-added and the gain iscontrolled, thereby the gain control corresponding to the total sum ofrespective received light outputs in the time division by the switchbecomes possible.

Also the timing of detecting the values of the received light outputs bythe detecting means can be set as follows. At first, phase of individualreceived light outputs changed by the switch is shifted by the phaseshifter, and the output waveform after the phase shifting is shaped intorectangular wave by the waveform shaping section. Then wavelength withthe rectangular wave being at high level is reduced by the triggercircuit, and the fall time is fitted to the peak time of the receivedlight outputs. Thereby the peak value can be detected with respect tothe phase of the received light output itself with high precision.

Also in the switch changing section, when the reference signal withrespect to the time of the switch changing becomes prescribed number,the allowance signal of detection is generated. The allowance signal isrectangular wave with length, corresponding to one period of thereference signal, for example, with respect to the rise of the referencesignal at the n periods (n: integer) after the switch is changed. Forexample, a synchronous circuit is installed, and the AND operationbetween rectangular wave with length corresponding to one period of thereference signal and short rectangular wave passing through the triggercircuit is carried out in the synchronous circuit, and as a result, thetiming pulse of the peak detecting is generated. In the detecting means,the received light outputs are sampled at the rise time of the timingpulse, and the received light outputs at the fall time are held as thepeak value.

Further, in the detecting means, the voltage level detecting sectiondetects the voltage level of each channel of the time division outputvoltage obtained at the selection time of the preceding channel andsupplies the detected voltage level to a control unit, and the controlunit compares amount of the voltage level of each channel detected inthe voltage level detecting section and supplies the succeeding channelchanging signal to the changing circuit so that channels are selected inthe order of amount of the voltage level at next time.

Thus at the channel selecting time, since the voltage level of eachchannel is selected in the order of amount of the voltage level obtainedpreviously, such state is prevented that the voltage level of thechannel changed and selected at first is too small or the voltage levelof the channel is nearly zero, and such state can be avoided that thetiming in the A/D conversion of the time division output voltage isshifted and the decision of the channel voltage and the noise voltagebecomes difficult, thereby the relative angle data outputted from thesignal processing unit always becomes correct.

The above and further objects and novel features of the invention willmore fully appear from the following detailed description when the sameis read in connection with the accompanying drawings. It is to beexpressly understood, however, that the drawings are for purpose ofillustration only and are not intended as a definition of the limits ofthe invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a circuit block diagram showing a relative angle detectingdevice in the first embodiment of the invention;

FIG. 2 is a circuit block diagram showing a relative angle detectingdevice in the second embodiment of the invention;

FIG. 3 is a circuit block diagram showing a relative angle detectingdevice in the third embodiment of the invention;

FIG. 4 is a circuit block diagram showing a relative angle detectingdevice in the fourth embodiment of the invention;

FIG. 5 is a circuit block diagram showing a relative angle detectingdevice in the fifth embodiment of the invention;

FIG. 6(A) is a waveform chart showing plural received light detectionvoltages;

FIG. 6(B) is a diagram showing sinusoidal wave by adding plural receivedlight detection voltages;

FIG. 6(C) is a waveform chart showing reference signal S1 by waveformshaping of sinusoidal wave;

FIG. 7(A)-(H) is a waveform chart showing sample/hold operation of peakvalue in peak detecting means;

FIG. 8 is a waveform chart showing each received light detection voltagethrough a band pass filter and peak value being held;

FIG. 9 is an appearance perspective view of a remote input device usinga relative angle detecting device of the invention;

FIG. 10 is a sectional view showing a part of the input device shown inFIG. 9;

FIG. 11 is a front view of 4-divided light receiving sections of theinput device; and

FIG. 12 is a block configuration diagram showing a relative angledetecting device in the sixth embodiment of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Embodiments of the present invention will be described referring to theaccompanying drawings as follows.

A relative angle detecting device of the embodiments is installed to aremote input device as shown in FIGS. 9 to 11 where input informationsuch as coordinate data is given from an input device 3 to a device bodyhaving a screen 1.

In the remote input device shown in FIGS. 9 to 11, a reference lightmodulated in constant frequency (the intensity varying regularly inconstant frequency) is emitted from a light source 2a at the side of thedevice body having the screen 1 and detected by the 4-divided lightreceiving sections 5a, 5b, 5c, 5d of a reception element 5 installed tothe input device 3. Within the input device 3, a detection current basedon received light amount in each light receiving section is convertedinto voltage, and based on the detection voltage, operation of{(Ru+Rd)-(Lu+Ld)}/(Ru+Lu+Rd+Ld) and operation of{(Ru+Lu)-(Rd+Ld)}/(Ru+Lu+Rd+Ld) are carried out. Thereby angle (θx, θy)with respect to the screen 1 of the Z-axis extending vertically from thefront surface of the input device 3 (including variation information ofthe inclination θx and θy) is detected, further the X-Y coordinates onthe screen 1 at the position of the Z-axis intersecting the screen(including information regarding the moving distance on the X-Ycoordinates) are calculated.

The X-Y coordinates information or angle information (θx, θy) operatedin the input device 3 is transmitted as information data regarding thedirection with respect to the device body (screen 1) of the input device3 to the device body by wire telegraphy or radio telegraphy.

Data such as coordinates or angle transmitted from the input: device 3are sent to a main CPU of the device body and processed there, and basedon the data, for example, a cursor 8 displayed on the screen 1 is moved.That is, if the direction of the Z-axis (angle θx and θy) of the inputdevice 3 is varied with respect to the screen 1, in response tovariation, the information data are given from the input device 3 to thedevice 3 to the device body and the demodulated in the device bodythereby the cursor mark 8 on the screen 1 is moved. Thereby drawing onthe screen 1 becomes possible or the cursor mark 8 can be fitted to anyposition displayed on the screen 1.

Also the input device 3 is provided with a click switch or otheroperation switch (operation member), and also operation information(operation data) of each switch is transmitted to the device body.Therefore the cursor mark 8 for example is fitted to any position on thescreen 1 and the switch of the input device 3 is operated then, therebythe ON or OFF input to the switch mark displayed on the screen 1 becomespossible. Also the operation member includes a power source switch orthe like.

FIG. 1 is a block diagram showing the first embodiment of a relativeangle detecting device.

In FIG. 1, a light source 2a for emitting a reference light is shown,and as shown in FIG. 9, the light source 2a is installed to the side ofthe device body such as a computer or a game device. Also circuits otherthan the light source 2a in FIG. 1 are all mounted on the input device3.

A reception element 5 has 4-divided light receiving sections 5a, 5b, 5c,5d similar to those shown in FIG. 11. Received light output(photoelectric conversion output) from each light receiving section issupplied to the current/voltage converters 11a, 11b, 11c, 11d. Amongindividual received light outputs Lu, Ru, Ld, Rd of the 4-divided lightreceiving sections 5a, 5b, 5c, 5d of the reception element 5, twooutputs are combined and added and the received light outputs due to theadding are supplied to respective current/voltage converters 11a-11d. InFIG. 1, the individual light receiving sections 5a-5d for adding thereceived light outputs from the individual light receiving sections incombination such as (Ru+Rd) are not shown.

The added output (Ru+Rd) is supplied to the current/voltage converter11a and converted into received light output voltage V1, and the output(Lu+Ld) is supplied to the current/voltage converter 11b and convertedinto the received light output voltage V2. Also the output (Lu+Ru) issupplied to the current/voltage converter 11c and converted into thereceived light output voltage V3, and the output (Lu+Rd) is supplied tothe current/voltage converter 11d and converted into the received lightoutput voltage V4.

A time division switch 12 is installed at next stage of each of thecurrent/voltage converters 11a-11d. Received light output voltages V1-V4passing through the current/voltage converters 11a-11d are changed andoutputted in order in definite period by the time division switch 12.The changing timing of the time division switch 12 is set by a switchchanging section 13. In the embodiment of FIG. 1, in order to generate areference signal S1 of switch changing timing by the switch changingsection 13, an adder 14, a band pass filter 15 and a waveform shapingsection 16 are installed.

Each received light output voltage V1-V4 subjected to time, division bythe time division switch 12 is amplified by a variable gain amplifier 17and passes through a band pass filter 18 and is supplied to peakdetecting means 19. In the embodiment: of FIG. 1, the peak detectingmeans 19 is a sample/hold circuit. As means for generating a samplingpulse S2 supplied to the sample/hold circuit, a phase shifter 21, awaveform shaping section 22, a trigger circuit 23 and a synchronouscircuit 24 are installed on position (a) at the rear stage of the bandpass filter 18 and at the front stage of the peak detecting means 19.

Peak voltage V1p-V4p of each of the received light output voltages V1-V4detected by the peak detecting means 19 is converted into digital valueby an analog/digital converter 25 and then is supplied to a CPU 26. TheCPU 26 controls the relative angle detecting device as a whole shown inFIG. 1, and acts as arithmetic means operating based on the peak value(peak voltage) converted into the digital value. Also the CPU 26 asarithmetic means is provided internally with a buffer memory for storingthe peak voltage temporarily, or the buffer memory is externallyinstalled to the CPU 26.

Next, operation of the relative angle detecting device shown in FIG. 1will be described.

A reference light of infrared radiation is emitted from the light source2a installed to the device body. The reference light has intensityvarying alternately in constant frequency f1. That is, in the devicebody, an oscillation section for oscillating constant frequency isinstalled, and the light source is modulated by this frequency anddriven, and infrared light of constant frequency f1 is emitted from thelight source 2a.

As shown in FIG. 11, in each of the light receiving sections 5a to 5d ofthe reception element 5 installed at the input device 3, a referencelight narrowed down by a diaphragm 6 is received and the received lightoutputs (photoelectric conversion outputs) Lu, Ru, Ld, Rd correspondingto the light receiving area are obtained.

Every two of the above-mentioned received light outputs are combined andadded by the adder, and received light outputs by adding of (Ru+Rd),(Lu+Ru), (Lu+Ru), (Ld+Rd) respectively are converted into voltage by thecurrent/voltage converters 11a-11d thereby the received light outputvoltages V1, V2, V3, V4 corresponding to the added values are obtained.

Each of the received light output voltages V1-V4 is voltage havingwaveform shown in FIG. 6(A). Respective received light output voltagesV1-V4 are fitted to each other in the phase, and different in the leveldepending on the light receiving area of the light receiving sections5a-5d. In the adder 14, the received light output voltages V1-V4 areadded, and in the band pass filter 15, unnecessary frequency other thanthe frequency f1 is removed, and sinusoidal waveform of the frequency f1shown in FIG. 6(B) is obtained. The sinusoidal wave is subjected towaveform shaping by the waveform shaping section 16 constituted by across comparator or the like, and a reference signal (reference-clock)S1 of rectangular wave shown in FIG. 6(C) is obtained.

The reference signal S1 is supplied to the switch changing section 13.The switch changing section 13 is mainly constituted by a counter, whichcounts the pulse number of rectangular wave of the reference signal S1.When the count value becomes a definite value, a changing signal S3 issupplied to the time division switch 12, and every time the timedivision switch 12 receives the changing signal 53, channels are changedin the order of CH1, CH2, CH3, CH4, CH1, CH2, . . . . When the timedivision switch 12 is changed to CH1, the received light output voltageV1 is outputted. Also when the time division switch 12 is changed toCH2, CH3, CH4, the received light output voltages V2, V3, V4 areoutputted respectively.

The received light output voltages outputted in order in definite periodby the time division are amplified by the variable gain amplifier 17 andsubjected to filtering by the band pass filter 18 where unnecessaryfrequency component other than the frequency f1 is removed.

FIG. 8 shows the received light output voltages V1-V4 immediately afterthe filtering by the band pass filter 18. As shown in FIG. 8, in theswitch changing section 13, every time pulse of rectangular wave of thereference signal S1 is counted 16 pulse, the changing signal S3 issupplied to the time division switch 12. Therefore the received lightoutput voltage of the frequency f1 is changed every 16 periods by thetime division switch 12. That is, the time division switch 12 as shownin FIG. 8 is changed to channels CH1, CH2, CH3, CH4, thereby thereceived light output voltages V1, V2, V3, V4 are outputtedcorresponding to 16 periods.

Next, peak value (peak voltage) V1p-V4p of each of the received lightoutput voltages V1-V4 shown in FIG. 8 is detected by the peak detectingmeans 19 as a sample/hold circuit:.

FIG. 7(A) shows received light output voltage (any of V1-V4) of sometime point at position (a) between the band pass filter 18 and the peakdetecting means 19. The received light output voltage to the position(a) is supplied intact to the peak detecting means 19 and also to thephase shifter 21. The phase shifter 21 advances the received lightoutput voltage by period corresponding to 45 degrees. FIG. 7(B) showssinusoidal waveform Sa advanced by period of 45 degrees.

The waveform shaping section 22 is mainly constituted by a comparator,and the threshold level by the comparator is shown by SL2. FIG. 7(C)shows rectangular wave Sb subjected to waveform shaping by the waveformshaping section 22. The trigger circuit 23 is one-shot trigger circuit,and duty factor of high level and low level of the rectangular wave Sbis varied by the trigger circuit 23 and one-shot pulse Sc is generated.The one-shot pulse Sc becomes a pulse rising at (ii) in synchronizationwith the rise of the rectangular wave Sb and falling at (iii) after thetime T1. In-the trigger circuit 23, the time T1 is determined to 1/8 (45degrees) of one period of the waveform of the frequency f1.Consequently, the fall of the one-shot pulse Sc is coincident with thepeak position P of the sinusoidal wave of the received light outputvoltage shown in FIG. 7(A). In addition, at the time point of passingthrough the trigger circuit 23, as shown in FIG. 7(D), the one-shotpulse Sc of one piece is generated every one period of the receivedlight output voltage.

Next, FIG. 7(E) shows a reference signal (reference clock: S1 subjectedto waveform shaping by the waveform shaping section 16 and supplied tothe switch changing section 13. The reference signal S1 is generatedbased on the waveform by adding received light output voltages V1-V4,and its period is substantially coincident with that of the receivedlight output voltage (FIG. 7(A)) at the position (a). Also the thresholdlevel of the comparator in the waveform section 16 is shown by SL1 inFIG. 7(A) for convenience.

The switch changing section 13 is mainly constituted by a counter, andif the count value becomes value corresponding to 16 periods, the timedivision switch 12 is changed by the changing signal S3, and the timingof changing the time division switch 12 is synchronous with the rise ofthe rectangular pulse of the reference signal S1. In the counter of theswitch changing section 13, the rectangular pulse of the referencesignal S1 is counted from the time immediately after supplying thechanging signal S3 to the time division switch 12, and insynchronization with the rise of next reference signal S1 that the countvalue becomes eight, an allowance signal S4 of peak detection issupplied to the synchronous circuit 24. As shown in FIG. 7(F), theallowance signal S4 is rectangular pulse with length of the time T2, andthe time T2 is coincident with one period of the reference signal S1.

That is, in the switch changing section 13, after changing the timedivision switch 12, time corresponding to eight periods of the referencesignal S1 passes, and the allowance signal S4 is generated so that highlevel continues by one period (time T2) from the moment of the ninthpulse rising to the moment of the tenth pulse rising in the rectangularpulse of the reference signal S1, and the allowance signal S4 issupplied to the synchronous circuit 24. Or by the counter of the switchchanging section 13, the allowance signal by one shot is supplied tothis synchronous circuit 24 respectively at the time of the ninth pulserising and at the time of the tenth pulse rising, and the signal S4 ofrectangular wave as shown in FIG. 7(F) may be generated within thesynchronous circuit 24.

The synchronous circuit 24 is mainly constituted by AND gate, andlogical sum of the one-shot pulse Sc passing through the trigger circuit23 and the allowance signal S4 is operated by the AND gate, and as aresult of the logical sum, a sampling pulse S2 shown in FIG. 7(G) isformed. The one-shot pulse Sc shown in FIG. 7(D) rises every one periodof the waveform of FIG. 7(B), and by passing through the synchronouscircuit 24, one-shot pulse Sc other than that rising between the ninthpulse and the tenth pulse of the reference signal S1 is removed.

In the sample/hold circuit of the peak detecting means 19, as shown inFIG. 7(H), the received light output voltage inputted from the position(a) is sampled in synchronization with rise of the sampling pulse S2,and voltage at the falling time of the sampling pulse S2 is held. Sincethe pulse length T1 of one-shot pulse in FIG. 7(D) is set to 1/8 of oneperiod, the peak value P of the received light output voltage can bedetected and the value is held.

According to the above-mentioned circuit configuration, as shown in FIG.8, after the time division switch 12 is changed to each channel, thepeak voltage immediately after lapse of the eight periods of thereceived light output voltage is detected and held. As shown in FIG. 8,immediately after changing the time division switch 12, initial voltageoutput in each channel varies due to transient phenomenon of the switchchanging. Consequently, as above described, after lapse of eight periodsafter changing the time division switch 12, the received light outputvoltage is sampled and the peak value (peak voltage) is held, therebythe peak voltage V1p, V2p, V3p, V4p of each of the received light outputvoltages V1-V4 can be detected correctly.

Also as shown in FIG. 8, channel changing by the time division switch 12is carried out every 16 periods of the received light output voltage,and the peak holding is carried out immediately after lapse of eightperiods after the channel changing. Therefore the output time of thepeak voltage V1p, V2p, V3p, V4p varying stepwise corresponds to 16periods being the same as that of the channel changing of the timedivision switch 12. In addition, the peak holding may be carried outafter lapse of the prescribed period after changing the time divisionswitch 12, and need not be necessarily carried out after lapse of eightperiods. However, considering variation of the output of transientphenomenon after the channel changing, it is preferable that thesampling is carried out after lapse of six periods, seven periods oreight periods in the stable state.

In the sample/hold operation as above described, the reference signal S1being self clock signal is generated based on the received lightdetection output received by the reception element 5, and the timedivision switch 12 is changed in synchronization with the referencesignal S1, and at the same time the peak voltage is held based on theallowance signal S4 in synchronization with the reference signal S1.Therefore the timing of holding the peak voltage is set with highprecision. Also since one-shot pulse Sc as the base of the samplingpulse is generated based on the waveform with the phase shifted by thephase shifter, the detection precision of the peak value of the receivedoutput voltage becomes high.

Next, the peak voltages V1p, V2p, V3p, V4p detected and held as shown inFIG. 8 are converted into digital values by the analog/digital converter25 and supplied to the CPU 26.

In the CPU 26, digital values of the peak voltages V1p, V2p, V3p, V4pare inputted in order at regular period intervals (every 16 periods ofthe frequency f1), and individual peak voltages are stored in sequenceto the internal memory or the external memory. After the digital valuesof the peak voltages V1p, V2p, V3p, V4p are stored in one set or severalsets to the memory, the values are read out and the digital value ofeach voltage is operated.

This operation is {(V1p-V2p)/(V1p+V2p)} and {(V3p-V4p)/(V3p+V4p)}. Byoperation of the former, the inclination component in θx direction ofthe input device 3 in FIG. 9 is obtained, and by operation of thelatter, the inclination component in θy direction of the input device 3is obtained. Based on the inclination components of θx and θy,coordinate information in terms of distance on the X-Y coordinates ofthe screen 1 is operated, and such information and further operationinformation of the operation member installed to the input device 3 aresupplied-to the device body by wire telegraphy or radio telegraphy.

Also the digital values of the peak voltages V1p, V2p, V3p, V4p storedin the memory by the CPU 26 are added, and the gain control signal 27 issupplied to the variable gain amplifier 17 by the added components.Thereby gain of the amplifier 17 for amplifying each received lightoutput voltage passing through the time division switch 12 iscontrolled. Although the peak voltages V1p, V2p, V3p, V4p are detectedin separate time bands respectively, these digital values are stored inthe memory and all peak voltages are added and the gain control signal27 is generated, thereby gain of the amplifier 17 is controlledcorrectly. That is, amplification in the same factor can be carried outto the individual received light output voltages V1, V2, V3, V4subjected to the time division.

Also in response to the added values of the digital values of the peakvoltages V1p, V2p, V3p, V4p in memory, the gain control is carried out,and control information is supplied to the side of the device body bythe signal transmission channel (radio telegraphy or wire telegraphy) 28thereby the emission intensity of the light source 2a emitting thereference light may be controlled.

Also the changing signal S3 is supplied from the switch changing section13 through the line 31 to the CPU 26, and the sampling pulse S2 issupplied from the synchronous circuit 24 through the line 32 to the CPU26. Thereby in the CPU 26, it can be recognized that the time divisionis carried out normally or the sample/hold is carried out.

FIG. 2 shows a relative angle detecting device in the second embodimentof the present invention.

Difference of this embodiment from the preceding embodiment shown inFIG. 1 will be described.

Each of received light output voltages V1-V4 changed by a time divisionswitch 12 passes through a variable gain amplifier 17 and is subjectedto filtering by a band pass filter 18, and from position (a) after thefiltering, voltage is taken out and sent to a waveform shaping section16. The waveform shaping section 16 is the same as the waveform shapingsection designated by the same reference numeral in FIG. 1, and servesto generate a reference signal S1. In the embodiment of FIG. 2, however,received light output voltage taken from the position (a) is subjectedto waveform shaping in the waveform shaping section 16, and a referencesignal S1 is generated and supplied to a switch changing section 13.

Other circuits are the same as those in FIG. 1, and in the switchchanging section 13, the reference signal S1 is counted and a changingsignal S3 and an allowance signal S4 of peak detection are generated.

In the embodiment of FIG. 2, the adder 14 and the band pass filter 15shown in FIG. 1 are omitted, and a band pass filter 18E serves also asthe band pass filter 15 to generate the reference signal S1.Consequently in FIG. 2, circuit configuration can be simplified.

Also in the embodiment shown in FIG. 2, since voltage taken fromposition immediately before peak detecting means 19 generates thereference signal S1, an allowance signal S4 in FIG. 7(F) generated basedon the reference signal S1 and one-shot pulse Sc generated based on thevoltage obtained from the position (a) are not largely shifted in thephase. For example, such problem is not liable to occur that one-shotpulse Sc deviates from the time T2 of the allowance signal S4 and asampling pulse Sc being AND output is not outputted.

Also in the embodiment of FIG. 1, since received light output voltages,V1-V4 before the time division are added in the adder 14 and a referencesignal S1 is generated by the waveform shaping section 16, when error isproduced in the time division in the time division switch 12, forexample, even if output is not obtained in any of channels, generationof the reference signal S1 is not affected. Consequently the generationof the reference signal S1 is continued and the time division switch 12.is continued to operate based on the reference signal S1. On the otherhand, in the embodiment shown in FIG. 2, if received light: outputvoltage is not obtained from any of channels due to the time divisionerror by the time division switch 12, no reference signal S1 isgenerated and changing of the time division switch 12 is stopped.

In order to continue the changing of the time division switch 12 always,the embodiment of FIG. 1 is preferable. However, if the time divisionerror is produced in the embodiment of FIG. 2, since the referencesignal S1 is not generated and the changing signal S3 is not sent to thetime division switch 12 and the allowance signal S4 is not supplied tothe synchronous circuit, no sampling pulse 32 is generated. Since suchinformation is supplied from the lines 31 and 32 immediately to the CPU26, in the CPU 26, it can be immediately recognized that the receivedlight detection error is produced, and processing such as stopping thewhole operation can be taken. From this point of view, also theembodiment shown in FIG. 2 becomes preferable.

FIG. 3 shows a relative angle detecting device in the third embodimentof the present invention.

In this embodiment, received light output voltage is taken from position(a) passing through a band pass filter 18 and subjected to waveformshaping by a waveform shaping section 16 thereby a reference signal S1is generated. The reference signal S1 is given by a line 33 to a CPU 26.Also phase of the received light detection voltage taken from theposition (a) is shifted by 45 degrees in a phase shifter 21, and thevoltage with phase shifted is subjected to waveform shaping by awaveform shaping section 22, and rectangular wave Sb shown in FIG. 7(C)is given by a line 34 to the CPU 26.

The CPU 26 functions not only as arithmetic means of the peak voltage ofthe received light detection voltage but also as a synchronous circuit24 with a switch changing section 13 and a trigger circuit 23 shown inFIG. 1 and FIG. 2. The function as the synchronous circuit 24 with theswitch changing section 13 and the trigger circuit 24 is exhibited byexecution of software.

By execution of software in the CPU 26, first, the reference signal S1is counted, and, for example, a changing signal S3 is supplied to thetime division switch 12 every 16 periods by a line 35 and changing ofeach channel of the time division switch 12 is carried out.

The same waveform processing as that shown in FIG. 7 is carried out bysoftware, and a sampling pulse S2 shown in FIG. 7(G) is generated andgiven from a line 36 to peak detecting means 19, and sampling of thereceived light output voltage and holding of the peak voltage arecarried out as shown in FIG. 7(H).

FIG. 4 shows a relative angle detecting device in the fourth embodimentof the present invention.

In this embodiment, function by software executed by a CPU 26 is furtherincreased, and function as a switch changing section. 13, a phaseshifter 21, a trigger circuit 23, a synchronous circuit 24 is exhibitedby the software.

Received light output voltage taken from position (a) is subjected towaveform shaping by a waveform shaping section 16, thereby a referencesignal S1 is generated and supplied through a line 33 to the CPU 26. Achanging signal S3 is supplied from the CPU 26 directly to a timedivision switch 12 through a line 35 and the time division switch 12 ischanged.

Also in the CPU 26, phase of the reference signal S1 is shifted by 45degrees and rectangular waveform of FIG. 7(C) is generated, and asampling pulse S2 is generated from the rectangular wave of FIG. 7(C)and the reference signal S1 as the base and supplied by a line 36 topeak detecting means 19 thereby sampling of the received light outputvoltage and holding of the peak voltage are carried out.

Also in circuit configuration shown in FIG. 4, the reference signal S1obtained from the waveform shaping section 16 is inputted to the CPU 26,and in the CPU 26, timing of rise and fall of the reference signal S1can be counted in a clock contained in the CPU and timing signal can begiven to the peak detecting means 19 every prescribed time. In the peakdetecting means 19, the peak value is detected based on the timingsignal. In this case, peak values V1p, V2p, V3p, V4p of the receivedlight output voltages can be detected in the peak detecting means 19,and peak values -V1p, -V2p, -V3p, -V4p at the minus side of bottomvalues of the received light output voltages can be detected as shown inbroken line in FIG. 8. Difference values (V1p)-(-V1p), (V2p)-(-V2p), . .. between the peak values at: the plus side V1p, V2p, . . . and the peakvalues at the minus side -V1p, -V2p, . . . are operated thereby the peakvalues of the received light output voltages can be detected with highprecision, even when fluctuation or vibration of the received lightoutput voltage exists due to influence of outer disturbing light ornoise with respect to the reference voltage (0V) shown in FIG. 8.

Also in the embodiments of FIG. 3 and FIG. 4, by software executed inthe CPU 26, other waveform processing is possible.

For example, the peak detecting means 19 may be not a sample/holdcircuit but a peak/hold circuit. In the CPU 26, first, the changingsignal S3 is supplied to the time division switch 12 based on thereference signal S1 given from the waveform shaping section 16, and thenthe reference signal S1 is counted thereby after lapse of eight periodsafter the time division changing, the timing (i) of rise of the ninthreference signal S1 can be recognized (refer to FIG. 7(E)). Also byshifting phase of the reference signal S1 by 45 degrees within the CPU26, the timing (ii) of rise of the one-shot pulse Sc immediately after(i) can be determined, and further by counting the clock contained inthe CPU, the time T1 can be measured and the timing (iii) of fall of theone-shot pulse Sc can be known. Holding signal is supplied from the line36 to the peak detecting means 19 being peak/hold circuit fitting to thetiming (iii). Thereby the peak value of the received light outputvoltage can be held by the peak detecting means 19.

Further in a relative angle detecting device of the fifth embodiment asshown in FIG. 5, received light output voltage passing through a bandpass filter 18 is converted into digital value by an analog/digitalconverter 25 and then is supplied to a CPU 26, and in the CPU 26, basedon reference signal S1 from a waveform shaping section 16, setting ofthe detection timing of the peak value of the received light outputvoltage and the detection of the peak value may be carried out bysoftware.

Next, the sixth embodiment of the present invention will be described indetail using FIG. 12.

As shown in FIG. 12, a computer (controlled type image display device)51 is provided with a CRT (cathode ray tube, i.e., display unit) 53 fordisplaying an image, a light emitting section 52 disposed on peripheralportion of the CRT 53, for example, on the upper side thereof, and alight signal reception section 54. A portable input device 55 has wholeconfiguration in long rectangular parallelepiped, and a detectingsection (not: shown) is installed at the front surface of the inputdevice 55. The detection section is constituted by a reception element56 provided with 4-divided light receiving sections 56a to 56d made ofphoto diode for example, and a diaphragm (not shown) having arectangular aperture and a visible light cut filter (not shown)respectively disposed at the front surface side of the reception element56. In the 4-divided light receiving sections 56a to 56d, the lightreceiving sections 56b and 56d are connected to a current/voltageconverter 57a so that output currents thereof are added, and the lightreceiving sections 56a and 56c are connected to a current/voltageconverter 57b so that output currents thereof are added. Also the lightreceiving sections 56a and 56b are connected to-a current/voltageconverter 57c so that output currents thereof are added, and the lightreceiving sections 56c and 56d are connected to a current/voltageconverter 57d so that. output currents thereof are added. Output of eachof the current/voltage converters 57a to 57d is connected separately tothe stationary contact terminal side of a changing switch (changingcircuit) 58 of one circuit and four contacts, and a movable contactterminal of the changing switch 58 is connected to each input of asignal processing unit 60 and a voltage level detection section 64. Thechanging switch 58 is connected to a switch changing control unit 59,and contacts are changed by control of the switch changing control unit59. Although not shown, the signal processing unit 60 is providedinternally with a variable gain amplifier, a band pass filter, a peakholding circuit, e.g., a sample/hold circuit and an analog/digitalconverter, and output of the signal processing unit 60 is connected to acontrol unit 62. Output of the band pass filter within the signalprocessing unit 60 is connected to input of a waveform shaping circuit61, and output of the waveform shaping circuit 61 and output of a leveldetection section 64 are connected to the control unit 62 respectively.The control unit 62 is connected to the switch control unit 59 and alight signal transmission section 63 respectively.

In this case, regarding the three directions represented by thethree-dimensional orthogonal coordinates, if the length direction ofthe-portable input device 55 is made the Z-axis direction and the twodirections orthogonal to the Z-axis are made the X-axis direction andthe Y-axis direction respectively, the 4-divided light receivingsections 56a to 56d constituting the reception element 56 are arrangedso that the light receiving sections 56a and 56b and the light receivingsections 56c and 56d are arranged in the X-axis direction, and also thelight receiving sections 56a and 56c and the light receiving sections56b and 56d are arranged in the Y-axis direction.

The relative angle detecting device of the embodiment having theabove-mentioned configuration operates as follows.

Now, if an operator holds the portable input device 55 by hands and thedetecting section side is directed to the direction of the CRT 53(direction of the light emitting section 52), a reference light ofinfrared region of the frequency f emitted from the light source of thelight emitting section 52 is incident to the detecting section of theportable input device 55. In the incident reference light, first,visible light component is moved in a visible light cut filter (notshown), and next, the light incident amount is adjusted in a diaphragm(not shown) and then the reference light is irradiated to the 4-dividedlight receiving sections 56a to 56d constituting the reception element56. Then rectangular spot light determined by an aperture of thediaphragm is irradiated to the 4-divided light receiving sections 56a to56d, and current outputs I_(LU), I_(RU), I_(LD), I_(RD) corresponding tothe irradiation area of the spot light are outputted from the 4-dividedlight receiving sections 56a to 56d. Any of these current outputsI_(LU), I_(RU), I_(LD), I_(RD) includes the frequency f being the maincomponent of the reference light. Among these currents I_(LU), I_(RU),I_(LD), I_(RD), sum of current outputs (I_(RU) +I_(RD)) obtained in oneset of the light receiving sections 56a and 56c arranged in the Y-axisdirection is supplied to the current/voltage converter 57a, and sum ofcurrent outputs (I_(LU) +I_(LD) obtained in other set of the lightreceiving sections 56b and 56d arranged in the Y-axis direction issupplied to the current/voltage converter 57b respectively. Also sum ofcurrent outputs (I_(LU) +I_(RU)) obtained in one set of the lightreceiving sections 56a and 56b arranged in the X-axis direction issupplied to the current/voltage converter 57c, and sum of currentoutputs (I_(LD) +I_(RD)) obtained in other set of the light receivingsections 56c and 56d arranged in the X-axis direction is supplied to thecurrent/voltage converter 57d respectively. Each of the current/voltageconverters 57a to 57d converts input current into output voltage, andreceived light output voltages V1 to V4 are arranged to channels 1 to 4in respective outputs. Subsequently these received light output voltagesV1 to v4 are supplied to the changing switch 58, and in the changingswitch 58, by the switch changing control unit 59 operating in responseto changing signal supplied from the control unit 62, movable contactsare changed in prescribed period in the order as follows. Therefore thereceived light output voltages V1 to V4 are selected in time divisioninto time division output voltages by the changing switch 58, and thetime division output voltages are supplied to the succeeding signalprocessing unit 60. The time division output voltages supplied to thesignal processing unit 60 are first amplified in the variable gainamplifier with gain in response to the gain control voltage suppliedfrom the control unit 62, subsequently unnecessary frequency componentother than the frequency f is removed in the band pass filter. Furtherthe signal of the frequency f obtained in the output of the band passfilter is subjected to sampling and holding in the sample/hold circuit;subsequently the sampling voltage is converted into digital signal inthe analog/digital converter and the digital signal is supplied asrelative angle data to the control unit 62.

Also in the signal processing unit 60, the signal of the frequency fobtained in the output of the band pass filter is supplied to thewaveform shaping circuit 61, and when the signal of the frequency fbecomes the stable state after the channel changing of the changingswitch 58 is carried out, the waveform shaping circuit 61 in cooperationwith the control unit 62, generates trigger pulse or the like to beoutputted in coincidence with the coming state of the peak voltage, andin response to the trigger pulse or the like, the control unit 62supplies timing pulse or the like to command the start and the end ofsampling to the sample/hold circuit, and also supplies timing pulse orthe like to command the start or the end of digital conversion to theanalog/digital converter.

Then the sample/hold circuit starts sampling of the signal of thefrequency f obtained in the output of the band pass filter by timingpulse supplied from the control unit 62, and holds the sampling voltageobtained by the sampling. The sampling voltage becomes peak voltage inthe stable state indicating the amplitude peak of one signal period,after lapse of plural periods of the signal of the frequency f obtainedin the output of the band pass filter after the channel changing by thechanging switch 58 is carried out. Subsequently the analog/digitalconverter converts the sampling voltage held in the sample/hold circuitinto digital signal by timing pulse supplied from the control unit 62,and the relative angle-data obtained then is supplied to the controlunit 62.

The control unit 62 operates the relative angle data supplied insequence in response to changing of the changing switch 58, and when therelative angle data (digital peak voltage) led from the received lightoutput voltages V1, V2, V3, V4 are V1p, V2p, V3p, V4p respectively,{(V1p-V2p)/(V1p+V2p)} and {(V3p-V4p)/(V3p+V4p)} are operated. By theoperation of the former, inclination angle θx of the portable inputdevice 55 in the X-axis direction is estimated, and by the operation ofthe latter, the inclination angle θy of the input device 55 in theY-axis direction is estimated. Based on the estimated angle θx, θy, thecontrol unit 62 carries out coordinate calculation in terms of distanceon the X-Y coordinates of the display surface of the CRT 53, andsupplies the calculation result to the light signal transmission section63. The light signal transmission section 63 transmits the calculationresult with a light signal reception section 54 on the side of thecomputer 51, and based on the calculation result in the received lightsignal, the light signal reception section 54 carries out display in theform of a cursor mark or the like at desired portion of the displaysurface of the CRT 53.

In this case, when the operation suitably moves the detection section ofthe portable input device 55 held by hands substantially in parallel tothe display surface of the CRT 53, or suitably varies the angle withrespect to the display surface, the inclination angle θx in the X-axisdirection and the inclination angle θy in the Y-axis direction of theportable input device 55 are varied at any time, and in response to thevariation, the position of the cursor mark indicated on the displaysurface of the CRT 53 is varied at any time.

Next, the level detector 64 detects the voltage level of each channel inthe time division output voltage obtained at the output side of thechanging switch 58, and supplies the detected voltage level of eachchannel to the control unit 62. If the voltage level of each channel issupplied from the level detector 64, the control unit 62 compares theamount of the voltage level, and adjusts the channel changing signal tobe supplied to the switch changing control unit 59 next time based onthe comparison result, and channel of next time is selected in orderfrom larger amount of the voltage level. For example, at the selectionstate of channel of next time, regarding the voltage levels V1, V2, V3,V4 of channels 1 to 4 in the time division output voltage obtained atthe output side of the changing switch 58, if the order of the amount ofthose is in V3>V1>V4>V2 the channel changing signal is adjusted so thatchannel selection of next time is carried out in the order of channel 3,channel 1, channel 4, channel 2. Also if the order of the voltage levelsV1, V2, V3, V4 in channels 1 to 4 is not changed thereafter, the channelchanging signal is adjusted so that channel selection of still next timeis carried out in the order of channel 3, channel. 1, channel 4, channel2. on the other hand, if the order of the amount of the voltage levelsV1, V2, V3, V4 in channels 1 to 4 is changed, the channel changingsignal is adjusted so that channel selection of next time is carried outin the order according to the changing.

At the operation start of the relative angle detecting device, at first,since the voltage level of each channel is not yet supplied from thelevel detector 64 to the control unit 62, the channel changing signal tobe supplied to the switch changing control unit 59 becomes a channelchanging signal so that selection of channels is carried out in theprescribed order, for example, in the order of channel 1, channel 2,channel 3, channel 4.

Thus according to the embodiment, at channel selection state of everytime, the voltage level detection section 64 detects the voltage levelof each channel of the time division output voltage obtained at channelselection of preceding time, and the control unit 62 compares the amountof the voltage at each channel detected in the voltage level detectionsection 64 and supplies the channel changing signal of next time to theswitch changing control unit 59 so that channels are selected in theorder of the amount of the voltage level at next time, thereby suchstate can be avoided that the voltage level of channel selected at firstis too small or substantially zero. In this case, since gain of thesignal processing section 60 is controlled with respect to the A/Dconversion value in the channel with larger voltage level, the gain ofthe signal processing unit 60 is fixed within some region by the largervoltage level coming at first, thereby the timing of the A/D conversionbecomes stable and decision of the channel voltage and the noise voltagebecomes easy, and further the relative angle detection data outputtedfrom the signal processing unit 60 can always made correct.

In the embodiment as above described, although the description has beencarried out in an example that the controlled type informationprocessing unit 51 is a computer, the invention is not limited to thecase that the information processing unit 51 is a computer, but may beapplied also to other device having a display section, for example, agame device or an AV device.

Also in the embodiment, although the description has been made in anexample that the 4-divided light receiving sections 56a to 56d are usedas the reception element 56, the present invention is not limited to thecase that the reception element 56 is the 4-divided light receivingsections 56a to 56d but may be applied also to the case that thereception element is the 6-divided light receiving sections or the lightreceiving sections divided in other number. However, when the receptionelement 56 is set to the light receiving sections divided in numberother than 4, corresponding to the set number, the number of thecurrent/voltage converters 57a to 57d must be, of course, changed.

In the present invention as above described, since a plurality ofreceived light outputs can be processed by processing circuits havingthe same characteristics, ratio of the plurality of received lightoutputs can be detected with high precision.

Also in the present invention, when a plurality of received lightoutputs are subjected to time division, the timing of the dividing canbe set with high precision using a simple circuit.

Further in the present invention, when light from a light source withintensity varying in prescribed frequency is received, the peak value ofthe received light output can be detected in timing with high precision,and also when plural received light outputs are obtained in timedivision, the peak value can be detected at the stable state of thereceived light outputs thereby the peak value of the received lightoutputs can be detected correctly.

Further according to the present invention, the voltage level detectionsection 64 detects the voltage level of each channel of the timedivision output voltage obtained at channel selection of the precedingtime and supplies the detected voltage level to the control unit 62, andthe control unit 62 compares the amount of the voltage level of eachchannel detected in the voltage level detection section 64 and suppliesthe channel changing signal of next time to the changing circuit 58 sothat channels are selected in the order of the larger voltage level atnext time.

Consequently, at selection state of channels, since the voltage level ofeach channel is selected in the order of larger voltage level obtainedin the prescribed time, such state can be avoided that the voltage levelof channel changed and selected at first is too small or the voltagelevel of the channel is substantially zero, and effects are in thattiming of the A/D conversion in the time division output voltage isstabilized, that decision of the channel voltage and the noise voltagebecomes easy, and that the relative angle data outputted from the signalprocessing unit 60 can be made normally correct.

What is claimed is:
 1. An optical position detecting device comprising:acontrolled type information processing device; and an input device, saidcontrolled type information processing device comprising: a lightemitting section; a display section; and a first light receivingsection, said input device comprising having a housing: one second lightreceiving section composed of a plurality of light receiving elementsreceiving light from said light emitting section; a plurality ofcurrent/voltage converters for converting output current of saidplurality of light receiving elements in said one second light receivingsection into voltage; a changing circuit for selecting output voltagesof plural channels obtained in said plurality of current/voltageconverters in time division in response to channel changing signals, andfor generating time-division output voltages; a signal processing unitfor processing the time-division output voltages, and for generatingrelative angle data; a voltage level detecting section for detectingvoltage level of each channel in the time-division output voltages; anda control unit for forming coordinate signals by operating andcalculating the relative angle data, and for transmitting the coordinatesignals to said first light receiving section, wherein said control unitsupplies next channel changing signals to said changing circuit, so thatchannels are selected in the order of magnitude of voltage level of eachchannel detected in said voltage level detecting section.
 2. An opticalposition detecting device comprising:a light source: one light receivingsection comprised of a plurality of light receiving elements forreceiving light emitted from said light source and mounted on a housing,each of the light receiving elements generating a received light output;channel switching means for sequentially selecting the received lightoutputs from the plurality of light receiving elements, and foroutputting the received light outputs in a time-division manner inresponse to a switching signal; a signal processing section forprocessing each of the received light outputs from the channel switchingmeans and for generating relative angle data; level detecting means fordetecting an output level of each of the received light outputs receivedfrom said channel switching means; and a control section for calculatingrelative positional light receiving section between said light sourceand each of said light receiving section from the relative angle dataand for transmitting said switching signal to said channel switchingmeans; wherein said control section sends said switching signal suchthat said channels are selected in the order of the magnitude of eachoutput level of said light receiving elements in said one lightreceiving section detected by said level detecting section.